It is pretty widely known I am a Whelen fan, and probably have a personal bias towards liking their products. However, since I am not a dealer of new products made by any company and just buy, sell and trade older equipment, I feel like I really don't have a "car in the race" as far as the current state of companies in this industry.
Whelen, IMHO, is the least scared of trying new things. Many of their products go through several (usually backwards compatible) versions. I like to see that they innovate and advance the industry without losing touch with what is actually needed. Their halogen rotators were never the backbone of their product line but had several redesigns throughout the years as feedback on the units in the field was noted. Many companies would call the first generation "good enough" when it comes to a product that isn't their main line. While strobes were always the area where Whelen excelled, they were able to see the tide turning to LED and retrofitted current products with LEDs without making "just an old bar filled with new guts" like some other companies. As the technology developed their LED offerings took over for their strobes at a rate that didn't make their existing units in the field obsolete.
Their CORE control system is by far the most versatile and easy to build I have ever used, but they still offer "dumb lightheads" and electronic flashers. Their sirens can be fully integrated into a system or you can install a standalone unit. The product line is wide but not bloated. You can build any system you need from start to finish. Considering their commitment to quality and in house and ground up manufacturing, their pricing is in line with their quality and the industry.
As far as standing behind a product I have never had a company (except Sound Off) service discontinued or older model equipment that fails once out of warranty or due to abuse/misuse. I had a siren that a crew dumped an entire thermos of coffee into. For the cost of shipping plus $65 they repaired it and sent it back good as new. This siren was years out of warranty and had been preplaced by a new (but similar) model. You can't beat that kind of commitment to standing behind a product.
In my opinion Whelen comes as close to being a full design and manufacturing company as you can get in modern times without losing volume and causing skyrocketing prices.